Recently, functions of metal complex compounds such as photoreactive functions, electron-transfer functions, and physiologically active functions have been attracting attention, and a number of researches are being conducted by utilizing such functions. Further, researches on ligands that bind to coordination metal have also been conducted. As a representative ligand, a unidentate ligand such as ammonia, pyridine, and a cyanide ion, a bidentate ligand such as ethylenediamine, bipyridine, and glycinato, and a multidentate ligand having a coordination number of three or more such as ethylenediaminetetraacetic acid are known.
Bipyridine, which is a representative bidentate ligand, has a chelate ligand structure and a function of coordinating with a metal element. However, owing to poor solubility of bipyridine complexes in organic solvents, there has been a problem that the utility range of such a complex is extremely limited.
Patent Literature 1 discloses a compound in which a long-chain alkyl group such as a hexyl group, a pentyl group, an octyl group, and a decyl group is introduced into polybipyridine.